1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus equipped with a heating furnace, and more particularly, it relates to a method of controlling the temperature of a heating furnace and a method for manufacturing semiconductor devices.
2. Description of the Related Art
For instance, in a sheet-feed apparatus, a reactive gas is supplied to a heating furnace to form thin films on a substrate such as a silicon wafer while heating the interior of the heating furnace, in which the substrate is accommodated, at a prescribed temperature. In the manufacture of semiconductor devices, the temperature condition of the heating furnace is critical, and hence the accuracy of the temperature control has a great influence on the quality of thin films formed. A radiation thermometer can accurately measure the temperature of an object to be detected without contact therewith and has excellent response. Thus, the radiation thermometer has conventionally been used for the manufacture of semiconductor devices. In addition, Japanese Patent Application Laid-Open No. 5-190462 discloses a plasma CVD apparatus. In this CVD apparatus, a radiation thermometer is used to measure the temperature of a glass substrate. In order to correct errors in the measurements of the radiation thermometer due to infrared rays radiated from a susceptor, correlation data between the temperature of the susceptor and the temperature of the glass substrate to the temperature indication of the infrared radiation thermometer is set beforehand. The temperature of the glass substrate detected by the radiation thermometer is corrected in accordance with the temperature of the susceptor detected by a thermocouple based on the correlation data, so that the temperature of the susceptor is controlled by the thus corrected temperature of the glass substrate.
However, in a deposition processing apparatus such as a chemical vapor deposition (CVD) apparatus, in case where a radiation thermometer is arranged in a reaction chamber, thin films are deposited on the radiation thermometer itself. In addition, in case where the radiation thermometer is arranged outside the reaction chamber through a chamber window, deposition is made on the chamber window. In either case, accuracy in the temperature measurements reduces with the passage of time. Thus, even if corrections are carried out based on the correlation data between the temperature of the susceptor and the temperature of the glass substrate, errors in the measurements of the radiation thermometer itself increase as deposition processing is carried out repeatedly. As a result, even if the above-mentioned error corrections are carried out, it is impossible to detect the true temperature of the glass substrate and hence to perform highly accurate temperature control.
The present invention has been made in view of the above-mentioned circumstances, and has for its object to provide a temperature control method and a semiconductor device manufacturing method which are capable of performing excellent temperature control without reducing its control accuracy even if there takes place a change in the measurement error of a temperature sensor due to the deposition of thin films thereon or the like.
In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a temperature control method for performing temperature control based on a detected value of a control temperature sensor and a temperature control parameter. The temperature control method includes determining in advance a correction value for the temperature control parameter that changes in accordance with the progress of the processing of a substrate; and making the temperature control parameter to be changed in accordance with the correction value thus determined when the substrate is processed.
Preferably, the temperature control method further includes determining in advance a first temperature control parameter in an initial stage and a second temperature control parameter after a prescribed amout or number of processes have been carried out for a reference temperature sensor and the control temperature sensor; determining a change rate of the temperature control parameter from the first temperature control parameter, the second temperature control parameter and the number of processes performed; and making the temperature control parameter to be changed at the change rate.
In an embodiment, temperature control is carried out by making the temperature control parameter to be changed through correction at a prescribed interval. Here, note that the term xe2x80x9cprescribed intervalxe2x80x9d means any one of xe2x80x9cevery batchxe2x80x9d, xe2x80x9cevery several batchesxe2x80x9d and xe2x80x9cevery fixed period of timexe2x80x9d. In addition, the term xe2x80x9ctemperature control parameterxe2x80x9d means any one of xe2x80x9ca temperature correction valuexe2x80x9d (e.g., a difference between the measured value of the susceptor temperature (the measurement of the radiation thermometer) and the measured value of the heater temperature (the measurement of the thermocouple thermometer)), xe2x80x9ca PID constantxe2x80x9d and xe2x80x9can alarm constantxe2x80x9d. Such a correction can be made as follows. When the temperature control parameter is assumed to be a difference between the measured value of the temperature sensor (radiation thermometer) in which an error is caused and the measured value of a reference temperature sensor (thermocouple thermometer) which becomes a reference, for instance, a difference in the temperature control parameter before and after a prescribed number of processes (for instance, 100 batches) (i.e., a difference between the measured temperatures of the respective sensors before and after the processing) is acquired beforehand, and at the time of control operation, a more reliable temperature difference is obtained by using the ratio of the amount or number of processes thus far processed to the prescribed amount or number of processes as the processing proceeds. However, other corrections such as nonlinear approximation and so on may be carried out. Note that upon acquisition of the difference between the temperature control parameter values, the temperature of the furnace for instance is controlled so as to make substantially constant the measured values of the temperature sensor containing an error, whereas during control operation, control is performed in such a manner that the measured value of the temperature sensor containing an error is made equal to the prescribed temperature by using the temperature control parameter that has been corrected with the measured temperature of the temperature sensor being made as a reference.
Preferably, the control temperature sensor is a radiation thermometer arranged in a processing apparatus having a heater, and the reference temperature sensor is a thermocouple thermometer.
Since the temperature of an object to be controlled can be directly measured without any contact by using the radiation thermometer, the response of measurements is excellent and hence the temperature of the object to be controlled can be accurately controlled to a prescribed temperature in a short period of time. In addition, the thermocouple thermometer is subjected to a reduced change over time or reduced aging even in CVD processing, and hence it is possible to more accurately correct the control parameter based on measurements that change over time.
Preferably, the temperature control parameter is made to change by correction at a prescribed interval. Preferably, the prescribed interval may be any one of every batch, every several batches, and every fixed period of time.
Preferably, the radiation thermometer is arranged in the vicinity of a susceptor in a reaction chamber of the processing apparatus, whereby accuracy in temperature measurements can be improved, thus making it possible to enhance the temperature control accuracy.
Preferably, the processing apparatus comprises a CVD apparatus. Accordingly, in CVD processing, even if thin films are deposited on the radiation thermometer, temperature control can be carried out accurately.
With the above arrangement, by making the temperature control parameter to be changed in accordance with a change in the error of measurements of the temperature sensor, it is possible to perform the temperature control without reducing its control accuracy even if there takes place a change in the measurement error of the temperature sensor due to the deposition of thin films thereon, etc.
According to another aspect of the present invention, there is provided a method for manufacturing semiconductor devices in which the temperature of a heater arranged in a reaction chamber is controlled by using a temperature value detected by a control temperature sensor and a parameter for temperature control so that the temperature of a substrate is controlled to deposit thin films on the substrate, thus manufacturing a semiconductor device. The method includes determining in advance a correction value for the temperature control parameter that changes in accordance with the progress of the processing of said substrate, and making the temperature control parameter to be changed in accordance with the correction value thus determined when the substrate is processed.
With such a semiconductor device manufacturing apparatus using the above temperature control method, temperature control can be carried out with high accuracy, thus making it possible to manufacture semiconductor devices of excellent quality.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.